Using kdump
You can use kdump to create system dumps for instances of Linux® on IBM® Z.
Before you begin
For using kdump, you require:- A Linux kernel image that has been compiled with the common code kernel configuration options CONFIG_KEXEC, CONFIG_CRASH_DUMP, and CONFIG_PROC_VMCORE. If you want to enable validity checks for the kdump kernel, you also need the CONFIG_KEXEC_FILE option. This requirement applies to both, the production system for which kdump is set up and to the kdump image.
- An initial kdump RAM disk if required by the kdump kernel image.
- A kexec package with kdump support.
- A System z9® or later IBM Z® or LinuxONE server.
Advantages of kdump
kdump offers these advantages over other dump methods:- While writing the dump, you can filter out extraneous pages and compress the dump, and so handle large dumps in a short time.
- When writing dumps over a network, you can use existing file system facilities to share dump space among multiple Linux instances without special preparations.
Shortcomings of kdump
kdump has these drawbacks:
- kdump cannot be used for issues that occur before kdump is initialized, for example, for early boot problems. For such problems, use a stand-alone dump tool for Linux on z/VM® and for Linux in LPAR mode. For Linux on KVM, use virsh dump instead.
- kdump is not as reliable as the stand-alone dump tools. For critical systems, you can set up stand-alone dump tools as a backup, in addition to the kdump configuration (see Failure recovery and backup tools). For Linux on KVM, virsh dump can serve as the backup.
- For production systems that run in LPAR mode, kdump consumes memory (see Memory consumption)
Additional information
For more information on how to configure kdump for Red Hat® and SUSE distributions, see kdump recommendations . This topic explains, with examples, the kdump configuration, kernel page filtering, hardware-accelerated compression and how to debug the kdump setup.